There's nothing you need to do. All supported currencies are added to your account automatically after the registration.
However, in order to be able receiving cryptocurrency payments, you must generate your deposit addresses, which is very simple. Just select "Create new address" from the drop down menu next to the account name. Your account can have up to 10 addresses for each cryptocurrency.
To display your cryptocurrency deposit address simply click on the account name or select "Show my addresses" by clicking on "Actions" button next to the account name.
Any coins sent to these addresses will go straight to your Cryptonator account.